Proofreading 3D (Tracing)

What is Proofreading?

Proofreading is verifying and correcting AI-generated neuron segmentations. This is the team's namesake task — what Princeton Tracers were originally hired to do. We review automated reconstructions and fix errors where the AI incorrectly joined (merged) or separated (split) neurons.

Split/Merge Resolution is an integral part of proofreading. When two neurons are incorrectly joined, we perform a split operation. When a single neuron is fragmented into multiple segments, we perform a merge to reconnect them.

Why is it Important?

Automated segmentation algorithms are powerful but imperfect. False mergers and false splits in 3D neuron reconstructions can lead to incorrect connectivity data. Human proofreaders catch errors that AI cannot, ensuring the resulting connectome data is accurate enough for scientific analysis.

Three-Round Triage System

1. Quick Scan — Rapidly scroll through the neuron looking for obvious errors: large mergers, clearly detached fragments, and branches that don't belong. Flag anything suspicious.
2. Systematic Review — Work through each branch methodically. Check that branches originate from the correct soma, verify that thin processes aren't artifacts, and examine crossing fibers carefully for false mergers.
3. Verification — Confirm corrections are clean. Check that splits haven't orphaned legitimate branches. Verify merges haven't introduced new errors. Review flagged regions one final time.

Key Operations

• Split — Separate incorrectly merged neurons at the point of error
• Merge — Reconnect fragments of the same neuron
• Undo — Reverse an incorrect operation
• Flag — Mark ambiguous regions for expert review

Common Failure Modes

• Missing small branches during quick scan
• Accepting AI-generated mergers without verifying at branch points
• Over-splitting at ambiguous or low-contrast regions
• Ignoring crossing fibers where two neurons pass near each other
• Rushing Round 1 and missing errors that compound later

Tools Used